Shock absorber



Feb. 16, 1932. w. 'KdGsTRo'M SHOCK ABSORBER Filed Oct. 22, 1928- 5 Sheets-Sheet 1 fin;

INVENTOR lfr kfzam a/ 2) BY Feb. 16, .1932. A. w. KOGSTROM snocx ABSORBER Filed Oct. 22, 1928 5 Sheets-Sheet 2 Feb. 16, 1932. A. w. KOGSTR OM 1,345,290

- SHOCK ABSORBER Filed Oct. 22, 1928 5 Sheets-Sheet 4 INVENTOR ATTORNEY:

Feb. 16, 1932. A. WJKOGSTROM SHOCK ABSORBER Filed Oct. 212, 1928 5 Sheets-Sheet 5 ATTORNEY) TNE E STTEFSI Axel. W. noes'rnoivl; OFDETROIT, rajronrenn, AssIeNon :To. LEIGHTON DUNNING,

I or nETRoIr, MICHIGAN" I snocx A ssoRBnR v Applicationfi1edi0ctober22, 1'928. se i e; 314,003.

-This invention pertains to improvements" in hydraulic shock absorber-sand th e'general object of the invention is to provide ameans for producing a more effectlvecontrol of the 1 relative movements of the body and. axle members of a vehicle.

Another object is to provide a hydrtion and long life, the resistance of which remains substantially unchanged when the viscosity of the working liquidchange'sr Another object is to" provide a hydraulic shock absorberfora motor vehicle in which the effective controlling resistance is main- 'tained at a substantially predetermined value at any point in the movement ofthe parts thereof. and in whichthe-resistanceis independent of the variations in-the relative.

velocity of thebody and axle members of the vehicle. v l J Another object is'to provide anovel means by which the pressure in theworking cylinder of a hydraulic shock absorber is caused to rev n1ain at a substantially predetermined value during the working stroke of a plston and 1s hected by changes in the viscosity in the liquid or by the velocity of piston movements Another object is to provide a novel intake 1 valve construction for a hydraulic shock ab5 306011161 in which the leaking of the valve as result of the pitting of the valve and valvej seat is minimized.

Another object is to provide a cheap and f A novel means of supporting the inlet valve spring ofa hydraullc shock absorber.

shock absorber having anovel means for securing a piston actuating arm to a rockshaft A afiordntg a .(511.eap.-C011Smltt(3tl0n and a l in which the workin'gelements are shown in connection which is particularly appl cable 7 l to two way shock absorbers where the arm is first stressed mi one'dlre-ctlon and then viewtaken through the axis of the inlet Valve 56 sorber for ai'motor vehicle which will 'efieo cylinder of a'hydraulic shoc uli'c: shock absorber of relatively cheap construe:

tively dampen chattering of the vehicle axles when passing over a road having a washboarddsurfacej y A further objectis to afford a cheap and novel' means for preventin an oscillating absorber from moving from its seatduring the. suction strol ie of'the device. r y p The above being among the objectsof the a 7 7 to" features of construotlon andcombination of parts to be hereinafter described Withrefer-n present ihventionjthe sameconsists in certain ence to the accompanying drawings, and then claimed, having the above and other objects In the accompanying drawings Wl'llChlllUS:

trate suitable embodiments of the present in Y vention', and in which like numerals refer to like parts throughout the several different 7 x Fig. lisaside view of a preferred form of Y hydraulic shock. absorber attached in a repreviews,-

sentative manner to the frame-and axle of a motor vehicle. v i i v -Fig. 2 is asectional side view of the device shown in Fig. 1"which.embodies'certain tea tures' ofthe invention and in'whi'ch the workmg ele nen 'treine positions of movement.

3 isa section along theline 3.13'0f F igs 2 inwlnch'the moving elements of therdevice areshown 1n their neutral positlonts are shownin one of their ex; j

" Fig. .4 is a sectional side viewof a shock absorber showing another embodiment of the p I invention in which the working elements 55 Another Ob ect is to provide a: hydraulic shown in one oftheir extreme positions of ,movement. 2

Fig. .5is asection of the line=;5,5 of Fig. I

their neutralpositions;

, Fig. 6 is anenlarged fragmentary sectional; 1

for the shock'absorber shown'in Figs. 2 and 3.

Fig. 7 isvan enlarged plan view of the inlet valve seat taken ason the line :7.7;of Fig. 6.

Fig.8 is an enlarged fragmentary sectional *view taken throughthe axis of the discharge.

Fig. 9 is a sectional view taken on the line 9-9 of Fig. 8.

Fig. 10 is a sectional view taken on the line third form of discharge valve construction.

Fig. 13 is a view similar to Fig.4 butshowing. amodified armiconstruction in'which the.

arm co-operates with the spring for the discharge valve whereby to control the tension of the same to produce predeterminedpressureswithin the cylinder varying 1n accordance with theposition of the vehlcle' axle relative" to its frame. I

Figs. 14 and 15 illustrate modifications of the construction shown in Fig. 13. v

Fig. 16 is an enlarged partially broken view showing a preferred form oficonnection between the operating arm andv co-operating shaft. Hi

Fig. 17 isa plan view of the split .sleeve employed in the connection shown in Fig. 16

Fig. .18 is fragmentary. sectional ylew taken. axially through a cylinder and piston showing'a modifiedtype of discharge valve in connection with the piston. I Fig. 19 is a view similar to Fig. 18 and showing a slight modification thereof. Fig. 20 is a. sectional view taken axially through a cylinder and piston and shows a modified control means for the discharge valve. v v a In any vehicle, such as an automob le, which has springs interposed between the body and axles, the discomfort experle'nced by theoccupants and the racklngof the body are caused by unbalanced forces acting upon the'body.

These unbalanced forces are the direct cause offaccelerations or decelerations which are 7 synonymous with riding discomfort. The unbalanced forces. result from the vehic-lesprings being compressed or distended from their normal position as the vehicle passes over inequalities in the road. The extent to which the riding qualities of the vehi cle may beimproved by a shock absorberdepends substantially. upon itsability to oppose or neutralize the unbalanced spring forces in like proportion to their magnitude atany instant.

During certain relative movements ofthe axle and body it is impossible for the shock absorber to improve the riding comfort and" in fact'any resistance it may offer during these particular movements w1ll detract therefrom, as the d rection of the force applied by the shock absorber to the body could only be such as to add to the unbalanced force acting on the body.

For clearness in' thedescription the completefcycle of vehicle spring action may be considered as divided into four phases. Dur

ing the first phase of action when the car spring is being compressed from its normal position, its unbalanced force acts against the body in an upward direction and as any resistance offered by a shock absorber would be in such a direction as to add to the unbalanced spring force it follows that a shock absorber should offer no resistance during this action.

During the second phase of action the compressed springrecoils. from the position assumed at the' end of the first phase back to its normal position, and during this phase the unbalanced force of the spring is still in an upward direction as inphase one, but since thfe'body and axle are movlng away from each other v1t 1s poss1ble for a shock absorber to impose a resistance which will be in the 0pposite direction to the unbalanced spring. force; I It, therefore, follows that during: this second phase of action a shock absorber should oppose the relative movement of the car: body and axlewith a resistance whioh is at all times; in proportion-to the unbalanced spring force. v

During the third phase of the action-the axle and body are separating beyond. their normalposition,:andthe unbalanced force on the body is in a downward direction, and as any resistance during this phase ofniovement offered bya shockabsorber would add to this unbalanced force it follows that a shock abs. .sorber shoulclwork freely during this third phase shock. absorber. should resist this motion with a force which is proportionalto the unbalanced force at each instant.

To summarize, in order to improve'the rid;

7 ing of a vehicle to thefullest extent a shockab'sorber should not offer any resistance to the compression of the spring from its normal position but shouldfresist the movement. of the compressed spring back toward its nor.- mal' position in a degree proportionaltothe unbalanced spring. force acting; upon the body at any instant, and it should not resist the motion during. which the spring isdistending from its normalposition but during" the return of the distended spring to its normal position it should offer'a resistance to this movement which is opposite-and inpro-. portion to the downward unbalanced force acting on the body at any instant.

There is no discomfort invelocity as such; discomfort is the result ofacceleration or deing accelerations or decelerations in amotor vehicle are caused by the unbalanced spring forces and proportional thereto and indes pendent of the velocity of movement atzany instant, it therefore follows that the remedy, the resisting force of a shock absorber, should at each instant be in proportion to theunbalanced spring" forces and should be unaf- I p p I withthe movement, but-should rather offer a resistance somewhatless than this at'the bej ginning of the movement, and a substantially: greater resistance than'this as the axle nearsv fected by the velocity of the spring action.

One fault which is common to hydraulic shock absorbers to a greater or lessextent is that the resistance they offer to the relative movements of body and axle is considerably 7 I earlier mentioned in CODDGCtiOll with the cycle greater in cold weatherwhen the working liquid is more viscous thaniwhen the weather, 1s warm and it, therefore, follows that if a shock absorber is not to-be used in a' climate where the temperature remains-the same the year around it should have incorporated in its construction means for overcoming this objection. 1

Thus, since the discomfort is in proportion to the unbalanced spring forceat any,

instant, and since the unbalanced spring force.

is purely a function of the position of the aisle with respect to the body it followsthat during the phases of its helpful actionthe magnitude of the resisting force of theshock absorber should be a substantially unvaryingv direct function of the position of the aXle with respect to the frame at each instant and should be independent of the velocity of the action and should further be unaffected by,

temperature.

In defining the above the shock absorber, the riding comfort has been the main consideration, and it would conform closely to the ideal if the unsprung weight (weight of axles, wheels, etc.) was i negligible. 3 o 1 r The unsprung weight, particularly in motor vehicles, is great enough to cause the axles, wheels, etc., to bounce up and down to an undesirable extent at times; the recoil of the resilient tire causing an upward throw of the wheel, compressing the vehicle spring, which in turn hurls the wheel against the road surface and compresses the tire, which again recoils and throws the wheel into the air. This is the ob ect1onable action noticed as the axles chatter over a .washboard road surface, or when the' front axle gets into high speed tramp or shimmy. When axle chattering, tramp1ng-, or shimmybody. There results, however, alack of traction and attendant control of the vehicle, which introduces an element of danger."

Although the amplitude of theseoscillations is not usually very great, their dampening cycle of operation of requires considerably more holding power g on the partof the shock absorber for smaller celeration andsince the discomfort producmovementsof the axle to either side of its normal position thanif the riding comfort of the vehicle body were the only objective.

treme positions, it should not exert a resistance which diminishes in direct proportion v its normal position; For the same reasons first defined, the holding power of the shock absorber should be independent of'the veloc ity of the action, and-should further be unafiected bytemperature. 1

T Referring to the drawings andparticularly to Figs. 1 to 3 inclusive, inFig. 1 is shown' a typical installation of ashock absorber on a' motor vehicle having a frame and aXle'31 connected ,to thefrarne 30 by, a

: leaf spring 32 and shackle 33. The shockabsorber casing 34 may be secured. to the,

frame 30 by bolts such as 35 or other suitable means. The operating arm, 36 of the shock absorber is connected by a conventional link 37 to the sprin 32 adjacentthe point where the spring is connected tothe axle. 31, or the link may be connected directly to the axl'e3l. Referring to Figs; 2 and 3 itwill be seen that the casing 34- is of hollow construction having anopentop closed by a cap 38 suitably securedto the casing 34 by screws 39 or other suitable means. lVithin, the casing 34; and

adjacent the top thereof is suitably j ournalled a transverse shaft 42, one end of which pro jects out from the casing S la-11d to the outer end of'which is non-rotatably secured the opcrating arm 36. Suitable packing such as 43 is -preferably providedfor preventing leak- I upwardly into the casing; Within the cylinder 46 is slidably rec-eived'a piston l? having a pair of upwardly pro ecting spaced lugs or arms 48. v An arm 4.9 non-rotatably secured to the shaft 42 is pivotally connected 'at its free end to the lugs or arms 48 by a pin 50 whose axis lies in parallel relationship withrespe'ct to the shaft 42 and the pin 44-,

The head 45 is provided with openings 53 connecting the interiorv of the cylinder 46 withthe lower partof the casing,-and the opening 53-is normally closed'by the disc valve 54; which is constantly' urged against its seat by the coil; spring 55 constantly held -is, either forwardly or rearwardly.

under compressionbet ween the valve 54- the piston47'.

Referring new to Figs. 8 and 9 whichshow the construction of the outlet valve-to thecylinder indetaihit 'will beobserved thatthe pi ston- 47 is provided with" a central plug (id-having an upwardly projecting boss por tion 5? which extends up intothe-interiorof the piston. l -heplug 56 is provided with an axial opening-58 which extends up into' the boss 57 where it connects with cross passages 59'which extend through the boss portion 5'? above the upper surface of the end wall of the-piston '47. The boss portion 57 is sur spring 63 constantly heldundercompressi'on w,loetweentheflan e 64 on the cup 60 and the asindicated in Fig. 8. Nhen'the cup member 6O is in position to fully close the cross passage-s 59'and'therefore the escape of'liquid from the-cylinder 46, there is a small amount of clearance left between the end of the boss 57 and the inner end wall of the cup 60 so that the edge of the cup will at all times seat against the face of the plug 56 when the ,gvalveis in closed position. A plurality of V axially extending grooves 66 formed in the circumference of the boss 57 toconvey the static pressure from the cylinder to the closed end of the cup. The same effect may be obtained without the grooves by increas- 'ing'the clearance between the boss 57'and the cup 60. When the device is in its neutralposition, as illustrated in Fig. 3-the axes oft'he shaft 42 and. pins 44 and all he in the same ine or any other suitable liquid, to a pointpreferably above the top of the cylinder 46.

In operation, when the-spring 82is' being" either compressed or distended fromit-s normal position shown, the arm 49 is moved through the link 37, arm 36 and shaft 42 to rotateeither to one side or the other of its -;neutral vertical position in the casing, caus-- ing the cylinder 46 to rock. about the axis of the pin 44 and the piston to move away from thecylinder head 45. This movement of the piston causes a: suction within the cylinder 46 which lifts thevalve 54 from its seat and draws liquid into the-cylinder 46 through the rounded by an inverted cup-shaped valvemember which is urged downwardly to cover the'cross passages 59 lJY'IIlBiLDS of a coil shoulders out e inner side of the arms 48' ,-plane or, as indicated in the drawings, in veropenings 53', the resistance offered by the valve- 54 to-thus drawing inthe; liquid being substantially negligible; Thus the movement of the shock absorber'parts, while the andaxle 31 return from either" direction toward their normal position, the piston is moved towardthe cylinder head and'the inlet 'valvebeingclosed, the liquid within the cylinder isput under pressure which instantly rises-to a point where its pressure against the inner'surface of the closed end of the cup 60 is-great enough to cause it'to compress the outlet valve spring-63: and raise the end. of

said cup fromengagement. with the upper surface of tlieplhg- 5'6 anduncover the passages 59. WVhen' this happens the liquid" within the cylinder '46'fiows through the passage 58 and out through the transverse passages 59=totlieinterior ofthe' piston 47' where it freely escapes back into the casing 34'. It

will, ofcourse, be apparent that the cup valve 60 will move only high enough under pressure within the cylinder 46 so that by restricting the escape ofliquid through the passages 59tl1e pressure of the liquid within the cylinder 46 will be maintained at a substantially constant value. At the same time the'passages 58 and 59 are large enough to" permit any rate of flowof the liquid through them that may be met during normal operation of a motor vehicle without causing temporary increase in the pressure on the liquid withinthe cylinder 46 due to being restricted in its flow through such. passages.

The discharge valve shown in detail in Figs. 8 and 9 is designed to eliminate any possibility of the liquid forced through it from substantially reacting'against the cup valve 60 with a velocityefl'ect and thereby cause an added increase in pressure acting against the spring63. It will be obvious that if the flow of liquid from the cylinder 46 through the opening 58 were allowed to impinge directly against the closed end of the cup 60 at relative high velocity the kinetic energy of its flow would be added to the static pressure imparted to it by the piston 47 inits downwardmovement toraise the cup 60 to a greater extent than the pressure of the liquid itself would raise it. In such a case the effectivepressure within the cylinder 46 thereof when the passages 59 are not comstantiallynoresistance to such movement of the spring. When, however, the spring 32' pletely opened by the valve and this-lat eral reaction does notfof course, afiect the axlal pressure on the spring63 to any appref ciable extent. The grooves 66 beingoutside the direct path of how. of such liquid through the opening do not permit any appreciable reaction of the flow against the closed end or the cup 60, although they do convey the static of the cup 60. 1 r V p I V Inasmuch as the pressure of-theliquld against the piston remainsconstant during the discharge'stroke, theresistance oilered by the shock absorber at the end its arm 36' to the relative movement between the, car body and the axieis, at anypoint, a simple function of the liquidpressure upon the piston multiplied by the ratidof the gefiective tion, shown in Fig. 8, the effective length of its lever arm 49 changes'from a maxpressure from the cylinder to the closed endv the valve still remains tightdue to its contact with the other seat. Ineventthat both of the' seats 68, or more where moreare employed as may be found desirable, become pitted, the

high velocity of theleakage at a point on the outer seat is checked in the groove from whence the leaking liquid must necessarily have to find its way to aleakage point on the next seat. 1 This arduous course which the leaking liquid must pursue greatly obstructs its progress and renders this type of construc-' :tion much more eflicient thanthe'single seat type of valve. v

. v "Itlmayals'obe noted at this point that by employin thespring 55 compressed between the piston 47. and the valve 54 instead of the usual typeofinlet valve provided with a I stem slidably extending through its center, a

cheaper and much more eflicient-construction results inasmuch as such pin need Qnotfbe provided, which eliminates "the labor in volved in its "assembly and also eliminates 25 imum to zero It canheireadily demon- 1 po b l g h y 96 118- strated through a simple computation that t nt pi and e al Wh e h are the holding power ofthis shockabsorber mployed. ml issubstantially, in proportionto the unhal- Anothe ea u of t present mventlqon o anced force of the vehicle spring on theibod'y particular importance is the means; which I employ'gtorse'curing the arm 49 to the shaft 42.

at all points of its recoil movement froinits maximum state of compression hack to nor-' inal position, or fromitsmaximum statecf distention back to normal-position. 1 Itis important-tonote at this POlDttllB Figs. 2 and?) and which are shown in an enlarged View in Figs; 6 and 7: The uppersurface of the cylinder head eliradially outannular seats 68 separated by a groove 67. The upper edges of theseats 68he in the same horizontal plane as viewed in Fig. GJa-nd are preferably of narrow constructlon n and; 1m-- 70 overlying the groove 69. a

In operation, it will be apparent that as the piston 47 moves on its suction stroke thesuction within the cylinder 46 will cause the'valve 5-1 to raise against the pressure of the spring 55 and the liquid in the casing 34 will fiowup through the openings 53 out over theseat 68 into the groove 69 and then upwardly through the slots 70 into the interior of the cylinder l6. Experience has shown that it but a single narrow seat is employed for the valve 54:, the seat becomes pitted. in due time because "of impurities in the liquid, and thereby reduces the efficiency of the valve which becomes apparent on the pressure stroke of the piston.

In this construction, however, in theevent specific details of theinletvalve: shown in wardly of the headfrom theopenings 53'is provlded w th a pair of upstandlng spaced The I provided with a plurality of marginal slots As indicatediin detail in Figs. 16 and 17 the armed) is provided witha threaded opening v78 extending radially with respect to the shaft 42 and-only part way into the arm 49. hrom the opening 73 a smoothwalled opening 7 it extends'to the surfaceofthe shaft 42 and in axial alignmentwith the opening 73. The opening 7 e ,isvcontinued within the shaft l2-by a smooth wallediope'ning 75 of equal diameter.-

Received within the openings 7 L and 75 is a split cylindrical sleeve? 6 having an axially taperedinner surface. -r A plug 77 is threaded intothe opening? and is provided witha tapered end 78vwhichfis received within the tapered .hojre ofthesleeve'ifih It-will be apparent that as the plug :7 7 isscrewed inwardly the tapered 'end will be forced intothe sleeve 7 1:7 and will cause itQto spread so asto bear around, its entire outer surface against the wallscf the openings 74 and 75. Thisforms .in efiecta solid pin. connecting thearm 4:9 to

theshaft 421 The tapered end 78 of the plug 5 7 7 is -preferably serrated so as to insure the sleeve 'ZG turning With the plug 77 and thus eliminate any possibility of the sleeve-7 6 freezing in the openings 74 and 7 5 and pre- 1 vent ready disassembly of the arm and shaft.

It may be noted that the conventional form of attachment of these parts consists of a stud threaded into the arm and having a tapered end directly engaging the walls of a tapered recess in the shaft. Such form of r 3 impossible-in production to eliminate entirely allthe play between the threaded stud and the threaded opening, when such 'con-.

struction is employed in a shockabsorber actingtwo ways, the stud soon b'ecoinesloose in the arm and an undesirable play develops which is detrimental to the action ofthe shock absorber. With'the construction shown and herein described all reliance on .tho .threadedportion of the stud'tending' to resist relativerotation between the arm and shaft is dispensed with and instead such load is taken care of through the split sleeve 76 whose close engagement with the smooth Walls-of the openings'fll and 75 is assured.

In Figs. 4 and 5 a slight modification of theconstruction in Figs. 2 and 3is shown.

' The cylinder 46 in this case is provided with ahead 83 which is formed-to provide on its lower surface a spherical seat 84;. The bot tom of the casing 3,4jis;provided' withan upstanding projection .85 the upper surface of which is formed to the shape of apart ofa surface o'tasphere, and thersurface '84 of the cylinderlhead 83'is adapted to slidablybear thereon. Amodified form o'fpiston 8.61s preferablyein ployed inthis construction and is provi de d with an annular upwardly extending recess 87in which .oneend of the spring 88 is received, the spring 88 being constantlyheld .undercompression between the blind end of .therreeess S'Z-and-a seat-member89 carriedby theheadSEB anchprojecting above it. The seat member 8.9 'is provided Withepenings 90 .in

its-side .walls for the ready passage of; the koperating'fiuid and isprovided with a central struction shown in Figs. 4 and 5, asiwell as the constructions shown in Figs. 2 and' 3, may be reversed withrespe'ct to the cylinder and piston ;.t-hat is, thepiston may be secured "for swinging movement only, and the cylinder maybe secured for movement with the arm 4E9, without afiectingthe'action of the deviceLin any way whatsoever. It will also 'be "apparent that the relativepositions. ottlie inlet and outlet-"valves mayhereversed without "affecting the operation of the device, al- 'thoughut is preterableto have .theinlet valve ad acent the bottom of the ,cas'ingrather-than adjacent the:top, for-the reason that, there is less possibility of drawing. air'bubbles into thecylinder 46. It isalso apparent that other inversionsofmembers such as securing-the shaftA-Qto the frame member of the vehicle and oscillating the casing 34tby'ineans of an arm ,rigidlyattached to it will not depart from the principles of this invention.

In the devicesabove described in connection with the drawings, the-construction has been such as to maintain a constant pressure Withinthe cylinder -16 during all phases of the relative movement between it and the However, it may bev desirable n.

piston 4?. some cases to have a greater pressure in the cylinder during certain phases of the movement between the vehicle axle and the body than at other times, and, in'Figs. 13 to 15 inclusive I show means where this may be;

readily andautoniatically accomplished. indicated n Fig. 18 the spring 63, instead of being compressed between the shoulders '65 and the end wallofthe )iston 47 is held 1 under compression between the end wall of a cup 94' and the end wall of thG PISlZOII 47,

the cup 94; being axially slidably received within tie piston 47. The spring 63 forces the cup'Se against the ad acent end of the arm 49 and its axia-lposition and consequent, lysthe tension of the spring 63 is controlled by the particular configuration of the end of the arm which the end of the cup contact-s with during swinging or thearm 49. .In the construction shown .in Fig. 13- thearm 4:9 is provided with an extended or ro*ectin cam .L J to surface 95 in alignment'with the axis of the arm 49. TliGTESUl't-TS, as will readily be apparent, that whenthe axes'ofthe pins 44., 50

be moved to its closed position with respect to the end wall of'the piston 47, and the spring 63 will be inits positionof maximum compression. In such. a position of theparts .the'c'up valve will be urged against its seat with a greater force thanat any other point iiithe travel of the parts, and accord-- ingly a greater pressure will be exerted on the "liquid in the cylinder as the partsapproach their neutralv position. The holding force ofthe shocl: absorber will tliei'eforeincrease ;as the parts move toward their neutral position with this construction.

It will be apparent that the position of the cam-like projection on the arm 49 may be varied with respect to the end of the arm 49 so asvto obtain a maximum pressure in the cylinder l6, and thereforea maximum holding power'of the shock absorber at any particular point in the movement of the same.

For instance, it may be desired to have the shock absorber exert its maximum holding power at or about the time the vehicle spring begins to return from fully distended position. In such a case a projection 96 may be formed on the end of the arm 49 as indicated in Fig. '14 so that at this one particularpoint in the movement of the shock absorber, the pressure of the spring 63 and consequently "the pressure that may be built up within the and shaft 42 are in alignment the cup 84 will a cylinder 16 is of maximum value. On the other hand it may be desired to have the shock absorber exerting a maximum holding power approximately midway between its maximum movement in either direction and its neutral position, and it will be apparent that in such case a pair of projections such as is indicated at 97 in Fig. may be provided 11 the end of the arm 19 to eliect this result. It will also be apparent that the value ofthe holding power of the shoe; absorber at any particular point of its travel may be varied by the height or extent to which the projections on the end of the arm 49 projectv therefrom. i

In Figs. 11 and 12 I showmodified forms ot the discharge valve theactions of which are substa tially the same as that described in connections with the construction shown in Fig. 8. In Fig. 11 the boss57'instead of enough to prevent any material reaction of the jet of liquid passing through the opening 58 from impinging against the. closed end of the cup valve 60 and reacting against such closed end in addition to the static pressure of the liquid.

The same result is accomplished in a sligl1tly different way in the construction shown in Fig. 12. In this casea cup valve member 99 of slightly different construction is employed as shown. The boss 57is provided in its upper end with an enlarged recess 100 which is connected to the passages 58 and 59 by a small opening 101. The cup valve 99-h as secured thereto an axially inwardlv extending piston member 102 which is slidably re ceived within the recess 100. The pressure of the liquid in-the cylinder 46 is'transmitted through the openings 58 and 101 to the recess 100 where it reacts against the end ofthe piston 102 to move the valve 99 from its seat to uncover the passages 59. The particular advantage of this construction is that a lighter spring 63 be employed for urging the cup valve 99 toward its closed position than.

. member but yet is preferably small enough to effect a dash-pot action between the valve member and the boss 57 to prevent chattering of the valve. V V

Fig. 18 shows another form of discharge valve which functions substantially the same This opening, as well as the valves previously described and illustrated in Figs. 8 to 12 inclusive.

Referring to Fig. 18 it will be seen that upon a downward movement of the piston 115 the pressure of the liquid in the cylinder downward direction when the pressure of the liquid on its upper end is suliicient. to

overcome the force of the spring 107 which bears against the lower end of the valve through the plate 108 and urges the valve towards closed position. Upon such opening of the-'valve'the liquid is allowedqto escape between the valveseat member 109 and the sharp annular edge of the valve and thence through theports 116 inthe. members 109..

It :will be noted that the high velocity jet of liquid issuing through the passage 10 when the valve is open impinges upon the stationary valve seat 109 which is rigidly secured to the piston 115, and therefore does not react upon the valve 105 in such a manner asto add an additional force to the static, pressure enough to allow a clearance, underfthe enlarged head of thevalve at all times. .Any

pressure which might tend tobuild up in the recess ll below the head of the valve through leakage of *liquid between the cylindrical valve stem and its guide 111 is relieved by means of small ducts 113 extending from-the bottom of the recess 111 to ad acent the ports 116.

, It will be further noted that the cylindrical opening at the upper end of the valve seat 110 into which the annular extension of the upper'end of the valve 105 is fitted, acts as an effective dash pot which prevents the valve from chattering. In this construction the lower end of the valve spring 107 is shown seated against an annular ring 114 which is screwed tightly into piston 115.

In Fig. 19 I- show; another construction of the same type of valve as is shown in Fig. 18.

This valve functions in substantially the same manner as the valve shown in Fig. 18 and the principal difference in construction is that the recess 111 is made deeper in this case and a spring 117 isheld in compressed condition between the lower face ofthe enlarged head 106 of the valve and the bottom wall of the recess 111. a

In Fig. 20 I show a valve construction fact that the valve spring 118 which urges the discharge valve to a closed position exerts a variable instead of a fixed pressure uponthe valve. The lower end of the spring 118 bears against the holding ring 89 which is seated against the cylinderv bottom 15. It will be readily seen that as the piston 115 moves downwardly in the cylinder 45 the spring 1 18 becomes further compressed, thus establishing an increasing pressure of the liquid in the cylinder as the piston 19 moves downwardly during its. discharge stroke. In connection with the cylinder bottom 15 are shown the inlet passages 53, inlet valve seats 68, a disc type inlet valve 5%, and an inlet valve spring 119. This in let valve is constructed substantially the same as that shown in Figs. l and 5. With these last described discharge valve v constructions a duct 120 is formedin the valve 105 at the lower edge of the'guide member 110 to permit the escape of any air that might otherwise become trapped under the guide 110 and above thelower end of the valve.

To summarize, it will be apparent that with a shock absorber constructed in accordance with the present invention substantially no resistance is ofiered by it when the vehicle spring is either being compressed or distended from its normal position, and therefore does not add to the unbalanced forces acting on the ends of the spring at such times, but that it does resist the movement of the spring from either its compressed or distended position back to its normal" position and acts against theunbalanced forces at the ends of the spring at such time. It will also heapparent that when the shock absorber is resisting the action of they spring its holding power may be controlled by suitable design 7 of the parts asdescribed to exert a predetermined value regardless of the velocity of discharge or the viscosity of the liquid in the device'or theftemperature of the liquid. It will also be apparent that by employing the oscillating cylinder as described, substantially no lateral pressure is exerted by the piston on the walls of the cylinder as is true of so many conventional forms of hydraulic shock absorbers which are abject to relatively rapid wear due to the same.

Formal changes may be made in the specific embodiment of the invention described without departing from the spirit or substance of the broad invention, the scope of which is commensurate with the appended claims. What I clainiis: I a 1. A hydraulic shock absorber comprising, in combination, a liquid containing casing, a rock shaft j ournaled in said casing, a cylinder within said casing oscillatable about a line parallel to said rock shaft, an arm secured to said rock shaft, a piston in saidcylinder pivotally connected to said arm, the pivotal axis of the connection between said arm and piston lying in a plane common to the axis of said rock shaft and the pivotal axis of said cylinder when said shock absorber is in neutral posion, an inlet valve for said cylinder, and a spring controlled outlet valve for said cylinder through said piston, said outlet valve being so'constructed as to obviate velocity effects and adapted to maintain a predetermined pressure in said cylinder during discharge of liquid therefrom at any point in the path of travel of said piston and also to remain substantially unafiected by changes in the rate of discharge of said liquid from said cylinder or in the viscosity of said liquid.

2. Incombination with a pressure cylinder, a cylindricalprojection extending outwardly from a wall subjected to the pressure within said cylinder, said projection being provided with a passageway therein opening onto a side wall thereof and connected with the interior of said cylinder, a sleeve fitting over said projection for closing said passageway to the flow of fluid, means constantly urging said sleeve to passage closing position, said projection being provided with a cylindrical recess in the outer endthereof the inner end of which is in open communication with said passageway through a relatively small opening, a piston carried by said sleeve slidably received in said recess whereby the pressure transmitted to its face from the fluid in said passageway will act to move said sleeve to uncover said passageway, and theend of said sleeve being closed over'the' end of said proj ection whereby toform a dash pot to prevent chattering of said sleeve.

In a hydraulic shockabsorber, in combination, a liquid containing casing, an oscillating cylinder, a reciprocating piston in said cylinder, a rock shaft journaled in said casing, an arm secured to said rock shaft, said arm beingpivotally connected to said piston, an inlet valve for allowing the liquid to flow freely into the cylinder but preventing flow in the opposite direction, an outlet passage with a spring controlled outlet valve in said piston, and means for automatically varying the pressure of said outlet valve spring upon said outlet valve in relation to the position of saidrarm with respect to said casing.

4. In a hydraulic shock absorber, in. combination, a liquid containing casing, an oscillating cylinder therein, a piston reciprocable in said cylinder, a rock shaft ournaled in said casing, an arm secured to said rock shaft and ipivotally connected to said piston, an inlet valve for permittin flow of fluid into said cylinder, an outlet passage in said pistOn, avalve for said passage, and a spring held under compression between said arm and the last mentioned valve for constantly urging said last mentioned valve toward closed position.

5. In a hydraulic shock absorber, in combination, a liquid containing casing, an oscillating cylinder therein, a piston reciprocable in said cylinder, a rock shaft journaled in said casing, an arm secured to said rock shaft and pivotally connected to said piston, an inlet valve for permitting flow of fluid into said cylinder, an outlet passage in said piston, a valve for said passage, and a springheld- V j springs ofa motor vehicle, a shock absorber 7 under compression between said arm and the last mentioned valve for constantly urging said last mentioned valve toward closed position, the surface of said arm against which said spring is adapted to bear being formed to a cam-like shape whereby the pressure of said spring on said last mentioned valve will vary in accordance withthe angle between the axis of said piston and the longitudinal axis of said arm. p

6. A discharge valve fora pressure chamber having an opening in a wall thereof comprising,

the end surface of said flange being shapedto be acted upon by the pressure within. saidchamber in opposition to said spring means.

7. In combination with a pressure chamber having an opening through a wall thereof, said opening being provided with a cylindrical enlargement at its outer end, a valve member slidably fitting'in said opening and provided with an outwardly flanged end slidably fitting in said cylindrical enlargement, a valve seat member fixed relative to said wall overlying said opening, said flanged end of said valve member being internally cut away to form an annularrim adapted to contact against said seat member,said valvemember being provided with an opening therethrough for communicating the pressure within said chamber to said cut away portion of said valve member, yieldable means constantly urging said annular rim towards con-o tact with said valve seatmember, and means for relieving any pressure that may tend to build up in said enlargement between the bottom thereof and said flanged end. 7

8. In combination, a pair of relatively movable members cooperating to establish'a pressure chamber ofvariable volume, one of said members being provided with an opening therethrough, a valve member oooperating with said opening to control the escape of fluid from said chamber throughin combination, a tubular member slidably received in said opening, said tubu-:

relatively movable members whereby the thereof.

a. l amber varying inversely as the volume 9; In combination with the frame, 'axle'and operatively connected between said frame and axle comprising. a liquid containing cas ing; a pair of relatively movable members there n ,co-operatlng to form a pressure chamber of varying volume, said members arranged to effect an increase-of volume of.

said chamber upon movement of said axle to eitherside of itsnormal position and, a decrease of volume of said chamber upon return of-said axle to its normal position, means 7 for admitting liquid to said chamber upon increase of volume thereof Without exerting a substantial resistance of the flow of said liquid,'and means for resisting the escape of liquid from said chamberupon decreaseof:

volume thereof, the resisting effect of the last mentioned means varying inversely as the volume of said chamber and being independent of the rate of discharge of said liquid from saidchamber.

AXEL W. KOGSTROM.

said opening, and a spring constantly urging said valve member towards close'd position,

one end of said spring co-operating with said valve member and the other end of said spring being movable with the other of said 

